#include "test_tcp.h"

#include "lwip/priv/tcp_priv.h"
#include "lwip/stats.h"
#include "tcp_helper.h"
#include "lwip/inet_chksum.h"

#ifdef _MSC_VER
#pragma warning(disable: 4307) /* we explicitly wrap around TCP seqnos */
#endif

#if !LWIP_STATS || !TCP_STATS || !MEMP_STATS
#error "This tests needs TCP- and MEMP-statistics enabled"
#endif
#if TCP_SND_BUF <= TCP_WND
#error "This tests needs TCP_SND_BUF to be > TCP_WND"
#endif

/* used with check_seqnos() */
#define SEQNO1 (0xFFFFFF00 - TCP_MSS)
#define ISS    6510
static u32_t seqnos[] = {
    SEQNO1,
    SEQNO1 + (1 * TCP_MSS),
    SEQNO1 + (2 * TCP_MSS),
    SEQNO1 + (3 * TCP_MSS),
    SEQNO1 + (4 * TCP_MSS),
    SEQNO1 + (5 * TCP_MSS)
};

static u8_t test_tcp_timer;

/* our own version of tcp_tmr so we can reset fast/slow timer state */
static void
test_tcp_tmr(void)
{
    tcp_fasttmr();
    if (++test_tcp_timer & 1) {
        tcp_slowtmr();
    }
}

/* Setups/teardown functions */
static struct netif* old_netif_list;
static struct netif* old_netif_default;

static void
tcp_setup(void)
{
    struct tcp_pcb dummy_pcb; /* we need this for tcp_next_iss() only */

    old_netif_list = netif_list;
    old_netif_default = netif_default;
    netif_list = NULL;
    netif_default = NULL;
    /* reset iss to default (6510) */
    tcp_ticks = 0;
    tcp_ticks = 0 - (tcp_next_iss(&dummy_pcb) - 6510);
    tcp_next_iss(&dummy_pcb);
    tcp_ticks = 0;

    test_tcp_timer = 0;
    tcp_remove_all();
    lwip_check_ensure_no_alloc(SKIP_POOL(MEMP_SYS_TIMEOUT));
}

static void
tcp_teardown(void)
{
    netif_list = NULL;
    netif_default = NULL;
    tcp_remove_all();
    /* restore netif_list for next tests (e.g. loopif) */
    netif_list = old_netif_list;
    netif_default = old_netif_default;
    lwip_check_ensure_no_alloc(SKIP_POOL(MEMP_SYS_TIMEOUT));
}


/* Test functions */

/** Call tcp_new() and tcp_abort() and test memp stats */
START_TEST(test_tcp_new_abort)
{
    struct tcp_pcb* pcb;
    LWIP_UNUSED_ARG(_i);

    fail_unless(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);

    pcb = tcp_new();
    fail_unless(pcb != NULL);
    if (pcb != NULL) {
        fail_unless(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
        tcp_abort(pcb);
        fail_unless(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
    }
}
END_TEST

/** Call tcp_new() and tcp_abort() and test memp stats */
START_TEST(test_tcp_listen_passive_open)
{
    struct tcp_pcb* pcb, *pcbl;
    struct tcp_pcb_listen* lpcb;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct pbuf* p;
    ip_addr_t src_addr;
    err_t err;
    LWIP_UNUSED_ARG(_i);

    fail_unless(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);

    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));

    pcb = tcp_new();
    EXPECT_RET(pcb != NULL);
    err = tcp_bind(pcb, &netif.ip_addr, 1234);
    EXPECT(err == ERR_OK);
    pcbl = tcp_listen(pcb);
    EXPECT_RET(pcbl != NULL);
    EXPECT_RET(pcbl != pcb);
    lpcb = (struct tcp_pcb_listen*)pcbl;

    ip_addr_set_ip4_u32_val(src_addr, lwip_htonl(lwip_ntohl(ip_addr_get_ip4_u32(&lpcb->local_ip)) + 1));

    /* check correct syn packet */
    p = tcp_create_segment(&src_addr, &lpcb->local_ip, 12345,
                           lpcb->local_port, NULL, 0, 12345, 54321, TCP_SYN);
    EXPECT(p != NULL);
    if (p != NULL) {
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT(txcounters.num_tx_calls == 1);
    }

    /* check syn packet with short length */
    p = tcp_create_segment(&src_addr, &lpcb->local_ip, 12345,
                           lpcb->local_port, NULL, 0, 12345, 54321, TCP_SYN);
    EXPECT(p != NULL);
    EXPECT(p->next == NULL);
    if ((p != NULL) && (p->next == NULL)) {
        p->len -= 2;
        p->tot_len -= 2;
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT(txcounters.num_tx_calls == 1);
    }

    tcp_close(pcbl);
}
END_TEST

/** Create an ESTABLISHED pcb and check if receive callback is called */
START_TEST(test_tcp_recv_inseq)
{
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data[] = {1, 2, 3, 4};
    u16_t data_len;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    data_len = sizeof(data);
    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));
    counters.expected_data_len = data_len;
    counters.expected_data = data;

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);

    /* create a segment */
    p = tcp_create_rx_segment(pcb, counters.expected_data, data_len, 0, 0, 0);
    EXPECT(p != NULL);
    if (p != NULL) {
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT(counters.close_calls == 0);
        EXPECT(counters.recv_calls == 1);
        EXPECT(counters.recved_bytes == data_len);
        EXPECT(counters.err_calls == 0);
    }

    /* make sure the pcb is freed */
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

/** Create an ESTABLISHED pcb and check if receive callback is called if a segment
 * overlapping rcv_nxt is received */
START_TEST(test_tcp_recv_inseq_trim)
{
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data[PBUF_POOL_BUFSIZE * 2];
    u16_t data_len;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    const u32_t new_data_len = 40;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    data_len = sizeof(data);
    memset(data, 0, sizeof(data));
    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));
    counters.expected_data_len = data_len;
    counters.expected_data = data;

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);

    /* create a segment (with an overlapping/old seqno so that the new data begins in the 2nd pbuf) */
    p = tcp_create_rx_segment(pcb, counters.expected_data, data_len, (u32_t)(0 - (data_len - new_data_len)), 0, 0);
    EXPECT(p != NULL);
    if (p != NULL) {
        EXPECT(p->next != NULL);
        if (p->next != NULL) {
            EXPECT(p->next->next != NULL);
        }
    }
    if ((p != NULL) && (p->next != NULL) && (p->next->next != NULL)) {
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT(counters.close_calls == 0);
        EXPECT(counters.recv_calls == 1);
        EXPECT(counters.recved_bytes == new_data_len);
        EXPECT(counters.err_calls == 0);
    }

    /* make sure the pcb is freed */
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

static err_t test_tcp_recv_expect1byte(void* arg, struct tcp_pcb* pcb, struct pbuf* p, err_t err);

static err_t
test_tcp_recv_expectclose(void* arg, struct tcp_pcb* pcb, struct pbuf* p, err_t err)
{
    EXPECT_RETX(pcb != NULL, ERR_OK);
    EXPECT_RETX(err == ERR_OK, ERR_OK);
    LWIP_UNUSED_ARG(arg);

    if (p != NULL) {
        fail();
    }
    else {
        /* correct: FIN received; close our end, too */
        err_t err2 = tcp_close(pcb);
        fail_unless(err2 == ERR_OK);
        /* set back to some other rx function, just to not get here again */
        tcp_recv(pcb, test_tcp_recv_expect1byte);
    }
    return ERR_OK;
}

static err_t
test_tcp_recv_expect1byte(void* arg, struct tcp_pcb* pcb, struct pbuf* p, err_t err)
{
    EXPECT_RETX(pcb != NULL, ERR_OK);
    EXPECT_RETX(err == ERR_OK, ERR_OK);
    LWIP_UNUSED_ARG(arg);

    if (p != NULL) {
        if ((p->len == 1) && (p->tot_len == 1)) {
            tcp_recv(pcb, test_tcp_recv_expectclose);
        }
        else {
            fail();
        }
        pbuf_free(p);
    }
    else {
        fail();
    }
    return ERR_OK;
}

START_TEST(test_tcp_passive_close)
{
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data = 0x0f;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);

    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));
    counters.expected_data_len = 1;
    counters.expected_data = &data;

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);

    /* create a segment without data */
    p = tcp_create_rx_segment(pcb, &data, 1, 0, 0, TCP_FIN);
    EXPECT(p != NULL);
    if (p != NULL) {
        tcp_recv(pcb, test_tcp_recv_expect1byte);
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
    }
    /* don't free the pcb here (part of the test!) */
}
END_TEST

START_TEST(test_tcp_active_abort)
{
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    char data = 0x0f;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    LWIP_UNUSED_ARG(_i);

    memset(&txcounters, 0, sizeof(txcounters));

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);

    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));
    counters.expected_data_len = 1;
    counters.expected_data = &data;

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);

    /* abort the pcb */
    EXPECT_RET(txcounters.num_tx_calls == 0);
    txcounters.copy_tx_packets = 1;
    tcp_abort(pcb);
    txcounters.copy_tx_packets = 0;
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 40U);
    EXPECT(txcounters.tx_packets != NULL);
    if (txcounters.tx_packets != NULL) {
        u16_t ret;
        struct tcp_hdr tcphdr;
        ret = pbuf_copy_partial(txcounters.tx_packets, &tcphdr, 20, 20);
        EXPECT(ret == 20);
        EXPECT(tcphdr.dest == PP_HTONS(TEST_REMOTE_PORT));
        EXPECT(tcphdr.src == PP_HTONS(TEST_LOCAL_PORT));
        pbuf_free(txcounters.tx_packets);
        txcounters.tx_packets = NULL;
    }

    /* don't free the pcb here (part of the test!) */
}
END_TEST

/** Check that we handle malformed tcp headers, and discard the pbuf(s) */
START_TEST(test_tcp_malformed_header)
{
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data[] = {1, 2, 3, 4};
    u16_t data_len, chksum;
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct tcp_hdr* hdr;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    data_len = sizeof(data);
    /* initialize counter struct */
    memset(&counters, 0, sizeof(counters));
    counters.expected_data_len = data_len;
    counters.expected_data = data;

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);

    /* create a segment */
    p = tcp_create_rx_segment(pcb, counters.expected_data, data_len, 0, 0, 0);

    pbuf_header(p, -(s16_t)sizeof(struct ip_hdr));

    hdr = (struct tcp_hdr*)p->payload;
    TCPH_HDRLEN_FLAGS_SET(hdr, 15, 0x3d1);

    hdr->chksum = 0;

    chksum = ip_chksum_pseudo(p, IP_PROTO_TCP, p->tot_len,
                              &test_remote_ip, &test_local_ip);

    hdr->chksum = chksum;

    pbuf_header(p, sizeof(struct ip_hdr));

    EXPECT(p != NULL);
    EXPECT(p->next == NULL);
    if (p != NULL) {
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT(counters.close_calls == 0);
        EXPECT(counters.recv_calls == 0);
        EXPECT(counters.recved_bytes == 0);
        EXPECT(counters.err_calls == 0);
    }

    /* make sure the pcb is freed */
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST


/** Provoke fast retransmission by duplicate ACKs and then recover by ACKing all sent data.
 * At the end, send more data. */
START_TEST(test_tcp_fast_retx_recover)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data1[] = { 1,  2,  3,  4};
    char data2[] = { 5,  6,  7,  8};
    char data3[] = { 9, 10, 11, 12};
    char data4[] = {13, 14, 15, 16};
    char data5[] = {17, 18, 19, 20};
    char data6[TCP_MSS] = {21, 22, 23, 24};
    err_t err;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* disable initial congestion window (we don't send a SYN here...) */
    pcb->cwnd = pcb->snd_wnd;

    /* send data1 */
    err = tcp_write(pcb, data1, sizeof(data1), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data1) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    memset(&txcounters, 0, sizeof(txcounters));
    /* "recv" ACK for data1 */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 4, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(pcb->unacked == NULL);
    /* send data2 */
    err = tcp_write(pcb, data2, sizeof(data2), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data2) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    memset(&txcounters, 0, sizeof(txcounters));
    /* duplicate ACK for data1 (data2 is lost) */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(pcb->dupacks == 1);
    /* send data3 */
    err = tcp_write(pcb, data3, sizeof(data3), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* nagle enabled, no tx calls */
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(txcounters.num_tx_bytes == 0);
    memset(&txcounters, 0, sizeof(txcounters));
    /* 2nd duplicate ACK for data1 (data2 and data3 are lost) */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(pcb->dupacks == 2);
    /* queue data4, don't send it (unsent-oversize is != 0) */
    err = tcp_write(pcb, data4, sizeof(data4), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    /* 3nd duplicate ACK for data1 (data2 and data3 are lost) -> fast retransmission */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    /*EXPECT_RET(txcounters.num_tx_calls == 1);*/
    EXPECT_RET(pcb->dupacks == 3);
    memset(&txcounters, 0, sizeof(txcounters));
    /* @todo: check expected data?*/

    /* send data5, not output yet */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    /*err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);*/
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(txcounters.num_tx_bytes == 0);
    memset(&txcounters, 0, sizeof(txcounters));
    {
        int i = 0;
        do {
            err = tcp_write(pcb, data6, TCP_MSS, TCP_WRITE_FLAG_COPY);
            i++;
        } while(err == ERR_OK);
        EXPECT_RET(err != ERR_OK);
    }
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /*EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(txcounters.num_tx_bytes == 0);*/
    memset(&txcounters, 0, sizeof(txcounters));

    /* send even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* ...and even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* ...and even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* ...and even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);

    /* send ACKs for data2 and data3 */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 12, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    /*EXPECT_RET(txcounters.num_tx_calls == 0);*/

    /* ...and even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* ...and even more data */
    err = tcp_write(pcb, data5, sizeof(data5), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);

#if 0
    /* create expected segment */
    p1 = tcp_create_rx_segment(pcb, counters.expected_data, data_len, 0, 0, 0);
    EXPECT_RET(p != NULL);
    if (p != NULL) {
        /* pass the segment to tcp_input */
        test_tcp_input(p, &netif);
        /* check if counters are as expected */
        EXPECT_RET(counters.close_calls == 0);
        EXPECT_RET(counters.recv_calls == 1);
        EXPECT_RET(counters.recved_bytes == data_len);
        EXPECT_RET(counters.err_calls == 0);
    }
#endif
    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

static u8_t tx_data[TCP_WND * 2];

static void
check_seqnos(struct tcp_seg* segs, int num_expected, u32_t* seqnos_expected)
{
    struct tcp_seg* s = segs;
    int i;
    for (i = 0; i < num_expected; i++, s = s->next) {
        EXPECT_RET(s != NULL);
        EXPECT(s->tcphdr->seqno == htonl(seqnos_expected[i]));
    }
    EXPECT(s == NULL);
}

/** Send data with sequence numbers that wrap around the u32_t range.
 * Then, provoke fast retransmission by duplicate ACKs and check that all
 * segment lists are still properly sorted. */
START_TEST(test_tcp_fast_rexmit_wraparound)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    err_t err;
    size_t i;
    u16_t sent_total = 0;
    LWIP_UNUSED_ARG(_i);

    for (i = 0; i < sizeof(tx_data); i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* disable initial congestion window (we don't send a SYN here...) */
    pcb->cwnd = 2 * TCP_MSS;
    /* start in congestion advoidance */
    pcb->ssthresh = pcb->cwnd;

    /* send 6 mss-sized segments */
    for (i = 0; i < 6; i++) {
        err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
        EXPECT_RET(err == ERR_OK);
        sent_total += TCP_MSS;
    }
    check_seqnos(pcb->unsent, 6, seqnos);
    EXPECT(pcb->unacked == NULL);
    err = tcp_output(pcb);
    EXPECT(txcounters.num_tx_calls == 2);
    EXPECT(txcounters.num_tx_bytes == 2 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));

    check_seqnos(pcb->unacked, 2, seqnos);
    check_seqnos(pcb->unsent, 4, &seqnos[2]);

    /* ACK the first segment */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, TCP_MSS, TCP_ACK);
    test_tcp_input(p, &netif);
    /* ensure this didn't trigger a retransmission. Only one
    segment should be transmitted because cwnd opened up by
    TCP_MSS and a fraction since we are in congestion avoidance */
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == TCP_MSS + 40U);
    memset(&txcounters, 0, sizeof(txcounters));
    check_seqnos(pcb->unacked, 2, &seqnos[1]);
    check_seqnos(pcb->unsent, 3, &seqnos[3]);

    /* 3 dupacks */
    EXPECT(pcb->dupacks == 0);
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    test_tcp_input(p, &netif);
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(pcb->dupacks == 1);
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    test_tcp_input(p, &netif);
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(pcb->dupacks == 2);
    /* 3rd dupack -> fast rexmit */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    test_tcp_input(p, &netif);
    EXPECT(pcb->dupacks == 3);
    EXPECT(txcounters.num_tx_calls == 4);
    memset(&txcounters, 0, sizeof(txcounters));
    EXPECT(pcb->unsent == NULL);
    check_seqnos(pcb->unacked, 5, &seqnos[1]);

    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

/** Send data with sequence numbers that wrap around the u32_t range.
 * Then, provoke RTO retransmission and check that all
 * segment lists are still properly sorted. */
START_TEST(test_tcp_rto_rexmit_wraparound)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct tcp_pcb dummy_pcb_for_iss; /* we need this for tcp_next_iss() only */
    err_t err;
    size_t i;
    u16_t sent_total = 0;
    LWIP_UNUSED_ARG(_i);

    for (i = 0; i < sizeof(tx_data); i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = 0;
    tcp_ticks = 0 - tcp_next_iss(&dummy_pcb_for_iss);
    tcp_ticks = SEQNO1 - tcp_next_iss(&dummy_pcb_for_iss);
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* disable initial congestion window (we don't send a SYN here...) */
    pcb->cwnd = 2 * TCP_MSS;

    /* send 6 mss-sized segments */
    for (i = 0; i < 6; i++) {
        err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
        EXPECT_RET(err == ERR_OK);
        sent_total += TCP_MSS;
    }
    check_seqnos(pcb->unsent, 6, seqnos);
    EXPECT(pcb->unacked == NULL);
    err = tcp_output(pcb);
    EXPECT(txcounters.num_tx_calls == 2);
    EXPECT(txcounters.num_tx_bytes == 2 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));

    check_seqnos(pcb->unacked, 2, seqnos);
    check_seqnos(pcb->unsent, 4, &seqnos[2]);

    /* call the tcp timer some times */
    for (i = 0; i < 10; i++) {
        test_tcp_tmr();
        EXPECT(txcounters.num_tx_calls == 0);
    }
    /* 11th call to tcp_tmr: RTO rexmit fires */
    test_tcp_tmr();
    EXPECT(txcounters.num_tx_calls == 1);
    check_seqnos(pcb->unacked, 1, seqnos);
    check_seqnos(pcb->unsent, 5, &seqnos[1]);

    /* fake greater cwnd */
    pcb->cwnd = pcb->snd_wnd;
    /* send more data */
    err = tcp_output(pcb);
    EXPECT(err == ERR_OK);
    /* check queues are sorted */
    EXPECT(pcb->unsent == NULL);
    check_seqnos(pcb->unacked, 6, seqnos);

    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

/** Provoke fast retransmission by duplicate ACKs and then recover by ACKing all sent data.
 * At the end, send more data. */
static void test_tcp_tx_full_window_lost(u8_t zero_window_probe_from_unsent)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    err_t err;
    size_t i;
    u16_t sent_total;
    u8_t expected = 0xFE;

    for (i = 0; i < sizeof(tx_data); i++) {
        u8_t d = (u8_t)i;
        if (d == 0xFE) {
            d = 0xF0;
        }
        tx_data[i] = d;
    }
    if (zero_window_probe_from_unsent) {
        tx_data[TCP_WND] = expected;
    }
    else {
        tx_data[0] = expected;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* disable initial congestion window (we don't send a SYN here...) */
    pcb->cwnd = pcb->snd_wnd;

    /* send a full window (minus 1 packets) of TCP data in MSS-sized chunks */
    sent_total = 0;
    if ((TCP_WND - TCP_MSS) % TCP_MSS != 0) {
        u16_t initial_data_len = (TCP_WND - TCP_MSS) % TCP_MSS;
        err = tcp_write(pcb, &tx_data[sent_total], initial_data_len, TCP_WRITE_FLAG_COPY);
        EXPECT_RET(err == ERR_OK);
        err = tcp_output(pcb);
        EXPECT_RET(err == ERR_OK);
        EXPECT(txcounters.num_tx_calls == 1);
        EXPECT(txcounters.num_tx_bytes == initial_data_len + 40U);
        memset(&txcounters, 0, sizeof(txcounters));
        sent_total += initial_data_len;
    }
    for (; sent_total < (TCP_WND - TCP_MSS); sent_total += TCP_MSS) {
        err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
        EXPECT_RET(err == ERR_OK);
        err = tcp_output(pcb);
        EXPECT_RET(err == ERR_OK);
        EXPECT(txcounters.num_tx_calls == 1);
        EXPECT(txcounters.num_tx_bytes == TCP_MSS + 40U);
        memset(&txcounters, 0, sizeof(txcounters));
    }
    EXPECT(sent_total == (TCP_WND - TCP_MSS));

    /* now ACK the packet before the first */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 0, TCP_ACK);
    test_tcp_input(p, &netif);
    /* ensure this didn't trigger a retransmission */
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(txcounters.num_tx_bytes == 0);

    EXPECT(pcb->persist_backoff == 0);
    /* send the last packet, now a complete window has been sent */
    err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
    sent_total += TCP_MSS;
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == TCP_MSS + 40U);
    memset(&txcounters, 0, sizeof(txcounters));
    EXPECT(pcb->persist_backoff == 0);

    if (zero_window_probe_from_unsent) {
        /* ACK all data but close the TX window */
        p = tcp_create_rx_segment_wnd(pcb, NULL, 0, 0, TCP_WND, TCP_ACK, 0);
        test_tcp_input(p, &netif);
        /* ensure this didn't trigger any transmission */
        EXPECT(txcounters.num_tx_calls == 0);
        EXPECT(txcounters.num_tx_bytes == 0);
        /* window is completely full, but persist timer is off since send buffer is empty */
        EXPECT(pcb->snd_wnd == 0);
        EXPECT(pcb->persist_backoff == 0);
    }

    /* send one byte more (out of window) -> persist timer starts */
    err = tcp_write(pcb, &tx_data[sent_total], 1, TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(txcounters.num_tx_bytes == 0);
    memset(&txcounters, 0, sizeof(txcounters));
    if (!zero_window_probe_from_unsent) {
        /* no persist timer unless a zero window announcement has been received */
        EXPECT(pcb->persist_backoff == 0);
    }
    else {
        EXPECT(pcb->persist_backoff == 1);

        /* call tcp_timer some more times to let persist timer count up */
        for (i = 0; i < 4; i++) {
            test_tcp_tmr();
            EXPECT(txcounters.num_tx_calls == 0);
            EXPECT(txcounters.num_tx_bytes == 0);
        }

        /* this should trigger the zero-window-probe */
        txcounters.copy_tx_packets = 1;
        test_tcp_tmr();
        txcounters.copy_tx_packets = 0;
        EXPECT(txcounters.num_tx_calls == 1);
        EXPECT(txcounters.num_tx_bytes == 1 + 40U);
        EXPECT(txcounters.tx_packets != NULL);
        if (txcounters.tx_packets != NULL) {
            u8_t sent;
            u16_t ret;
            ret = pbuf_copy_partial(txcounters.tx_packets, &sent, 1, 40U);
            EXPECT(ret == 1);
            EXPECT(sent == expected);
        }
        if (txcounters.tx_packets != NULL) {
            pbuf_free(txcounters.tx_packets);
            txcounters.tx_packets = NULL;
        }
    }

    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}

START_TEST(test_tcp_tx_full_window_lost_from_unsent)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_tx_full_window_lost(1);
}
END_TEST

START_TEST(test_tcp_tx_full_window_lost_from_unacked)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_tx_full_window_lost(0);
}
END_TEST

/** Send data, provoke retransmission and then add data to a segment
 * that already has been sent before. */
START_TEST(test_tcp_retx_add_to_sent)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    char data1a[] = {  1,  2,  3};
    char data1b[] = {  4};
    char data2a[] = {  5,  6,  7,  8};
    char data2b[] = {  5,  6,  7};
    char data3[] = {  9, 10, 11, 12, 12};
    char data4[] = { 13, 14, 15, 16, 17};
    err_t err;
    int i;
    LWIP_UNUSED_ARG(_i);

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* disable initial congestion window (we don't send a SYN here...) */
    pcb->cwnd = pcb->snd_wnd;

    /* send data1 */
    err = tcp_write(pcb, data1a, sizeof(data1a), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_write(pcb, data1b, sizeof(data1b), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data1a) + sizeof(data1b) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    memset(&txcounters, 0, sizeof(txcounters));
    /* "recv" ACK for data1 */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 4, TCP_ACK);
    EXPECT_RET(p != NULL);
    test_tcp_input(p, &netif);
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(pcb->unacked == NULL);
    /* send data2 */
    err = tcp_write(pcb, data2a, sizeof(data2a), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_write(pcb, data2b, sizeof(data2b), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data2a) + sizeof(data2b) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    memset(&txcounters, 0, sizeof(txcounters));
    /* send data3 */
    err = tcp_write(pcb, data3, sizeof(data3), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(txcounters.num_tx_calls == 0);
    EXPECT_RET(txcounters.num_tx_bytes == 0);
    memset(&txcounters, 0, sizeof(txcounters));

    /* data3 not sent yet (nagle) */
    EXPECT_RET(pcb->unacked != NULL);
    EXPECT_RET(pcb->unsent != NULL);

    /* disable nagle for this test so data to sent segment can be added below... */
    tcp_nagle_disable(pcb);

    /* call the tcp timer some times */
    for (i = 0; i < 20; i++) {
        test_tcp_tmr();
        if (txcounters.num_tx_calls != 0) {
            break;
        }
    }
    /* data3 sent */
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data3) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    EXPECT_RET(pcb->unacked != NULL);
    EXPECT_RET(pcb->unsent == NULL);
    memset(&txcounters, 0, sizeof(txcounters));

    tcp_nagle_enable(pcb);

    /* call the tcp timer some times */
    for (i = 0; i < 20; i++) {
        test_tcp_tmr();
        if (txcounters.num_tx_calls != 0) {
            break;
        }
    }
    /* RTO: rexmit of data2 */
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data2a) + sizeof(data2b) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    EXPECT_RET(pcb->unacked != NULL);
    EXPECT_RET(pcb->unsent != NULL);
    memset(&txcounters, 0, sizeof(txcounters));

    /* send data4 */
    err = tcp_write(pcb, data4, sizeof(data4), TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    /* disable nagle for this test so data to transmit without further ACKs... */
    tcp_nagle_disable(pcb);
    err = tcp_output(pcb);
    EXPECT_RET(err == ERR_OK);
    /* nagle enabled, no tx calls */
    EXPECT_RET(txcounters.num_tx_calls == 1);
    EXPECT_RET(txcounters.num_tx_bytes == sizeof(data3) + sizeof(data4) + sizeof(struct tcp_hdr) + sizeof(struct ip_hdr));
    memset(&txcounters, 0, sizeof(txcounters));
    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

START_TEST(test_tcp_rto_tracking)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    err_t err;
    size_t i;
    u16_t sent_total = 0;
    LWIP_UNUSED_ARG(_i);

    for (i = 0; i < sizeof(tx_data); i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* Set congestion window large enough to send all our segments */
    pcb->cwnd = 5 * TCP_MSS;

    /* send 5 mss-sized segments */
    for (i = 0; i < 5; i++) {
        err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
        EXPECT_RET(err == ERR_OK);
        sent_total += TCP_MSS;
    }
    check_seqnos(pcb->unsent, 5, seqnos);
    EXPECT(pcb->unacked == NULL);
    err = tcp_output(pcb);
    EXPECT(txcounters.num_tx_calls == 5);
    EXPECT(txcounters.num_tx_bytes == 5 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));
    /* Check all 5 are in-flight */
    EXPECT(pcb->unsent == NULL);
    check_seqnos(pcb->unacked, 5, seqnos);

    /* Force us into retransmisson timeout */
    while (!(pcb->flags & TF_RTO)) {
        test_tcp_tmr();
    }
    /* Ensure 4 remaining segments are back on unsent, ready for retransmission */
    check_seqnos(pcb->unsent, 4, &seqnos[1]);
    /* Ensure 1st segment is on unacked (already retransmitted) */
    check_seqnos(pcb->unacked, 1, seqnos);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == TCP_MSS + 40U);
    memset(&txcounters, 0, sizeof(txcounters));
    /* Ensure rto_end points to next byte */
    EXPECT(pcb->rto_end == seqnos[5]);
    EXPECT(pcb->rto_end == pcb->snd_nxt);
    /* Check cwnd was reset */
    EXPECT(pcb->cwnd == pcb->mss);

    /* Add another segment to send buffer which is outside of RTO */
    err = tcp_write(pcb, &tx_data[sent_total], TCP_MSS, TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    sent_total += TCP_MSS;
    check_seqnos(pcb->unsent, 5, &seqnos[1]);
    /* Ensure no new data was sent */
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(txcounters.num_tx_bytes == 0);
    EXPECT(pcb->rto_end == pcb->snd_nxt);

    /* ACK first segment */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, TCP_MSS, TCP_ACK);
    test_tcp_input(p, &netif);
    /* Next two retranmissions should go out, due to cwnd in slow start */
    EXPECT(txcounters.num_tx_calls == 2);
    EXPECT(txcounters.num_tx_bytes == 2 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));
    check_seqnos(pcb->unacked, 2, &seqnos[1]);
    check_seqnos(pcb->unsent, 3, &seqnos[3]);
    /* RTO should still be marked */
    EXPECT(pcb->flags & TF_RTO);
    /* cwnd should have only grown by 1 MSS */
    EXPECT(pcb->cwnd == (tcpwnd_size_t)(2 * pcb->mss));
    /* Ensure no new data was sent */
    EXPECT(pcb->rto_end == pcb->snd_nxt);

    /* ACK the next two segments */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 2 * TCP_MSS, TCP_ACK);
    test_tcp_input(p, &netif);
    /* Final 2 retransmissions and 1 new data should go out */
    EXPECT(txcounters.num_tx_calls == 3);
    EXPECT(txcounters.num_tx_bytes == 3 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));
    check_seqnos(pcb->unacked, 3, &seqnos[3]);
    EXPECT(pcb->unsent == NULL);
    /* RTO should still be marked */
    EXPECT(pcb->flags & TF_RTO);
    /* cwnd should have only grown by 1 MSS */
    EXPECT(pcb->cwnd == (tcpwnd_size_t)(3 * pcb->mss));
    /* snd_nxt should have been advanced past rto_end */
    EXPECT(TCP_SEQ_GT(pcb->snd_nxt, pcb->rto_end));

    /* ACK the next two segments, finishing our RTO, leaving new segment unacked */
    p = tcp_create_rx_segment(pcb, NULL, 0, 0, 2 * TCP_MSS, TCP_ACK);
    test_tcp_input(p, &netif);
    EXPECT(!(pcb->flags & TF_RTO));
    check_seqnos(pcb->unacked, 1, &seqnos[5]);
    /* We should be in ABC congestion avoidance, so no change in cwnd */
    EXPECT(pcb->cwnd == (tcpwnd_size_t)(3 * pcb->mss));
    EXPECT(pcb->cwnd >= pcb->ssthresh);
    /* Ensure ABC congestion avoidance is tracking bytes acked */
    EXPECT(pcb->bytes_acked == (tcpwnd_size_t)(2 * pcb->mss));

    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

static void test_tcp_rto_timeout_impl(int link_down)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb, *cur;
    err_t err;
    size_t i;
    const size_t max_wait_ctr = 1024 * 1024;

    /* Setup data for a single segment */
    for (i = 0; i < TCP_MSS; i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    pcb->cwnd = TCP_MSS;

    /* send our segment */
    err = tcp_write(pcb, &tx_data[0], TCP_MSS, TCP_WRITE_FLAG_COPY);
    EXPECT_RET(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 1 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    /* Force us into retransmisson timeout */
    for (i = 0; !(pcb->flags & TF_RTO) && i < max_wait_ctr; i++) {
        test_tcp_tmr();
    }
    EXPECT(i < max_wait_ctr);

    /* check first rexmit */
    EXPECT(pcb->nrtx == 1);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 1 * (TCP_MSS + 40U));

    /* still no error expected */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    if (link_down) {
        netif_set_link_down(&netif);
    }

    /* keep running the timer till we hit our maximum RTO */
    for (i = 0;  counters.last_err == ERR_OK && i < max_wait_ctr; i++) {
        test_tcp_tmr();
    }
    EXPECT(i < max_wait_ctr);

    /* check number of retransmissions */
    if (link_down) {
        EXPECT(txcounters.num_tx_calls == 1);
        EXPECT(txcounters.num_tx_bytes == 1 * (TCP_MSS + 40U));
    }
    else {
        EXPECT(txcounters.num_tx_calls == TCP_MAXRTX);
        EXPECT(txcounters.num_tx_bytes == TCP_MAXRTX * (TCP_MSS + 40U));
    }

    /* check the connection (pcb) has been aborted */
    EXPECT(counters.err_calls == 1);
    EXPECT(counters.last_err == ERR_ABRT);
    /* check our pcb is no longer active */
    for (cur = tcp_active_pcbs; cur != NULL; cur = cur->next) {
        EXPECT(cur != pcb);
    }
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}

START_TEST(test_tcp_rto_timeout)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_rto_timeout_impl(0);
}
END_TEST

START_TEST(test_tcp_rto_timeout_link_down)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_rto_timeout_impl(1);
}
END_TEST

static void test_tcp_rto_timeout_syn_sent_impl(int link_down)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb, *cur;
    err_t err;
    size_t i;
    const size_t max_wait_ctr = 1024 * 1024;
    const u16_t tcp_syn_opts_len = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_MSS | TF_SEG_OPTS_WND_SCALE | TF_SEG_OPTS_SACK_PERM | TF_SEG_OPTS_TS);

    /* Setup data for a single segment */
    for (i = 0; i < TCP_MSS; i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    err = tcp_connect(pcb, &netif.gw, 123, NULL);
    EXPECT_RET(err == ERR_OK);
    EXPECT_RET(pcb->state == SYN_SENT);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 40U + tcp_syn_opts_len);

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    txcounters.num_tx_calls = 0;
    txcounters.num_tx_bytes = 0;

    /* Force us into retransmisson timeout */
    for (i = 0; !(pcb->flags & TF_RTO) && i < max_wait_ctr; i++) {
        test_tcp_tmr();
    }
    EXPECT(i < max_wait_ctr);

    /* check first rexmit */
    EXPECT(pcb->nrtx == 1);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 40U + tcp_syn_opts_len); /* 40: headers; >=: options */

    /* still no error expected */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    if (link_down) {
        /* set link down and check what happens to the RTO counter */
        netif_set_link_down(&netif);
    }

    /* keep running the timer till we hit our maximum RTO */
    for (i = 0;  counters.last_err == ERR_OK && i < max_wait_ctr; i++) {
        test_tcp_tmr();
    }
    EXPECT(i < max_wait_ctr);

    /* check number of retransmissions */
    if (link_down) {
        EXPECT(txcounters.num_tx_calls == 1);
        EXPECT(txcounters.num_tx_bytes == 40U + tcp_syn_opts_len);
    }
    else {
        EXPECT(txcounters.num_tx_calls == TCP_SYNMAXRTX);
        EXPECT(txcounters.num_tx_bytes == TCP_SYNMAXRTX * (tcp_syn_opts_len + 40U));
    }

    /* check the connection (pcb) has been aborted */
    EXPECT(counters.err_calls == 1);
    EXPECT(counters.last_err == ERR_ABRT);
    /* check our pcb is no longer active */
    for (cur = tcp_active_pcbs; cur != NULL; cur = cur->next) {
        EXPECT(cur != pcb);
    }
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}

START_TEST(test_tcp_rto_timeout_syn_sent)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_rto_timeout_syn_sent_impl(0);
}
END_TEST

START_TEST(test_tcp_rto_timeout_syn_sent_link_down)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_rto_timeout_syn_sent_impl(1);
}
END_TEST

static void test_tcp_zwp_timeout_impl(int link_down)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb, *cur;
    struct pbuf* p;
    err_t err;
    size_t i;

    /* Setup data for two segments */
    for (i = 0; i < 2 * TCP_MSS; i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    pcb->cwnd = TCP_MSS;

    /* send first segment */
    err = tcp_write(pcb, &tx_data[0], TCP_MSS, TCP_WRITE_FLAG_COPY);
    EXPECT(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT(err == ERR_OK);

    /* verify segment is in-flight */
    EXPECT(pcb->unsent == NULL);
    check_seqnos(pcb->unacked, 1, seqnos);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == 1 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));

    /* ACK the segment and close the TX window */
    p = tcp_create_rx_segment_wnd(pcb, NULL, 0, 0, TCP_MSS, TCP_ACK, 0);
    test_tcp_input(p, &netif);
    EXPECT(pcb->unacked == NULL);
    EXPECT(pcb->unsent == NULL);
    /* send buffer empty, persist should be off */
    EXPECT(pcb->persist_backoff == 0);
    EXPECT(pcb->snd_wnd == 0);

    /* send second segment, should be buffered */
    err = tcp_write(pcb, &tx_data[TCP_MSS], TCP_MSS, TCP_WRITE_FLAG_COPY);
    EXPECT(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT(err == ERR_OK);

    /* ensure it is buffered and persist timer started */
    EXPECT(pcb->unacked == NULL);
    check_seqnos(pcb->unsent, 1, &seqnos[1]);
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(txcounters.num_tx_bytes == 0);
    EXPECT(pcb->persist_backoff == 1);

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    /* run timer till first probe */
    EXPECT(pcb->persist_probe == 0);
    while (pcb->persist_probe == 0) {
        test_tcp_tmr();
    }
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == (1 + 40U));
    memset(&txcounters, 0, sizeof(txcounters));

    /* respond to probe with remote's current SEQ, ACK, and zero-window */
    p = tcp_create_rx_segment_wnd(pcb, NULL, 0, 0, 0, TCP_ACK, 0);
    test_tcp_input(p, &netif);
    /* ensure zero-window is still active, but probe count reset */
    EXPECT(pcb->persist_backoff > 1);
    EXPECT(pcb->persist_probe == 0);
    EXPECT(pcb->snd_wnd == 0);

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    if (link_down) {
        netif_set_link_down(&netif);
    }

    /* now run the timer till we hit our maximum probe count */
    while (counters.last_err == ERR_OK) {
        test_tcp_tmr();
    }

    if (link_down) {
        EXPECT(txcounters.num_tx_calls == 0);
        EXPECT(txcounters.num_tx_bytes == 0);
    }
    else {
        /* check maximum number of 1 byte probes were sent */
        EXPECT(txcounters.num_tx_calls == TCP_MAXRTX);
        EXPECT(txcounters.num_tx_bytes == TCP_MAXRTX * (1 + 40U));
    }

    /* check the connection (pcb) has been aborted */
    EXPECT(counters.err_calls == 1);
    EXPECT(counters.last_err == ERR_ABRT);
    /* check our pcb is no longer active */
    for (cur = tcp_active_pcbs; cur != NULL; cur = cur->next) {
        EXPECT(cur != pcb);
    }
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}

START_TEST(test_tcp_zwp_timeout)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_zwp_timeout_impl(0);
}
END_TEST

START_TEST(test_tcp_zwp_timeout_link_down)
{
    LWIP_UNUSED_ARG(_i);
    test_tcp_zwp_timeout_impl(1);
}
END_TEST

START_TEST(test_tcp_persist_split)
{
    struct netif netif;
    struct test_tcp_txcounters txcounters;
    struct test_tcp_counters counters;
    struct tcp_pcb* pcb;
    struct pbuf* p;
    err_t err;
    size_t i;
    LWIP_UNUSED_ARG(_i);

    /* Setup data for four segments */
    for (i = 0; i < 4 * TCP_MSS; i++) {
        tx_data[i] = (u8_t)i;
    }

    /* initialize local vars */
    test_tcp_init_netif(&netif, &txcounters, &test_local_ip, &test_netmask);
    memset(&counters, 0, sizeof(counters));

    /* create and initialize the pcb */
    tcp_ticks = SEQNO1 - ISS;
    pcb = test_tcp_new_counters_pcb(&counters);
    EXPECT_RET(pcb != NULL);
    tcp_set_state(pcb, ESTABLISHED, &test_local_ip, &test_remote_ip, TEST_LOCAL_PORT, TEST_REMOTE_PORT);
    pcb->mss = TCP_MSS;
    /* set window to three segments */
    pcb->cwnd = 3 * TCP_MSS;
    pcb->snd_wnd = 3 * TCP_MSS;
    pcb->snd_wnd_max = 3 * TCP_MSS;

    /* send four segments. Fourth should stay buffered and is a 3/4 MSS segment to
       get coverage on the oversized segment case */
    err = tcp_write(pcb, &tx_data[0], (3 * TCP_MSS) + (TCP_MSS - (TCP_MSS / 4)), TCP_WRITE_FLAG_COPY);
    EXPECT(err == ERR_OK);
    err = tcp_output(pcb);
    EXPECT(err == ERR_OK);

    /* verify 3 segments are in-flight */
    EXPECT(pcb->unacked != NULL);
    check_seqnos(pcb->unacked, 3, seqnos);
    EXPECT(txcounters.num_tx_calls == 3);
    EXPECT(txcounters.num_tx_bytes == 3 * (TCP_MSS + 40U));
    memset(&txcounters, 0, sizeof(txcounters));
    /* verify 4th segment is on unsent */
    EXPECT(pcb->unsent != NULL);
    EXPECT(pcb->unsent->len == TCP_MSS - (TCP_MSS / 4));
    check_seqnos(pcb->unsent, 1, &seqnos[3]);
#if TCP_OVERSIZE
    EXPECT(pcb->unsent_oversize == TCP_MSS / 4);
#if TCP_OVERSIZE_DBGCHECK
    EXPECT(pcb->unsent->oversize_left == pcb->unsent_oversize);
#endif /* TCP_OVERSIZE_DBGCHECK */
#endif /* TCP_OVERSIZE */

    /* ACK the 3 segments and update the window to only 1/2 TCP_MSS.
       4th segment should stay on unsent because it's bigger than 1/2 MSS */
    p = tcp_create_rx_segment_wnd(pcb, NULL, 0, 0, 3 * TCP_MSS, TCP_ACK, TCP_MSS / 2);
    test_tcp_input(p, &netif);
    EXPECT(pcb->unacked == NULL);
    EXPECT(pcb->snd_wnd == TCP_MSS / 2);
    EXPECT(pcb->unsent != NULL);
    check_seqnos(pcb->unsent, 1, &seqnos[3]);
    EXPECT(txcounters.num_tx_calls == 0);
    EXPECT(txcounters.num_tx_bytes == 0);
    /* persist timer should be started since 4th segment is stuck waiting on snd_wnd */
    EXPECT(pcb->persist_backoff == 1);

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    /* call tcp_timer some more times to let persist timer count up */
    for (i = 0; i < 4; i++) {
        test_tcp_tmr();
        EXPECT(txcounters.num_tx_calls == 0);
        EXPECT(txcounters.num_tx_bytes == 0);
    }

    /* this should be the first timer shot, which should split the
     * segment and send a runt (of the remaining window size) */
    txcounters.copy_tx_packets = 1;
    test_tcp_tmr();
    txcounters.copy_tx_packets = 0;
    /* persist will be disabled as RTO timer takes over */
    EXPECT(pcb->persist_backoff == 0);
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == ((TCP_MSS / 2) + 40U));
    /* verify 1/2 MSS segment sent, 1/4 MSS still buffered */
    EXPECT(pcb->unsent != NULL);
    EXPECT(pcb->unsent->len == TCP_MSS / 4);
    EXPECT(pcb->unacked != NULL);
    EXPECT(pcb->unacked->len == TCP_MSS / 2);
#if TCP_OVERSIZE
    /* verify there is no oversized remaining since during the
       segment split, the remainder pbuf is always the exact length */
    EXPECT(pcb->unsent_oversize == 0);
#if TCP_OVERSIZE_DBGCHECK
    /* Split segment already transmitted, should be at 0 */
    EXPECT(pcb->unacked->oversize_left == 0);
    /* Remainder segement should match pcb value (which is 0) */
    EXPECT(pcb->unsent->oversize_left == pcb->unsent_oversize);
#endif /* TCP_OVERSIZE_DBGCHECK */
#endif /* TCP_OVERSIZE */

    /* verify first half segment */
    EXPECT(txcounters.tx_packets != NULL);
    if (txcounters.tx_packets != NULL) {
        u8_t sent[TCP_MSS / 2];
        u16_t ret;
        ret = pbuf_copy_partial(txcounters.tx_packets, &sent, TCP_MSS / 2, 40U);
        EXPECT(ret == TCP_MSS / 2);
        EXPECT(memcmp(sent, &tx_data[3 * TCP_MSS], TCP_MSS / 2) == 0);
    }
    if (txcounters.tx_packets != NULL) {
        pbuf_free(txcounters.tx_packets);
        txcounters.tx_packets = NULL;
    }
    memset(&txcounters, 0, sizeof(txcounters));

    /* ACK the half segment, leave window at half segment */
    p = tcp_create_rx_segment_wnd(pcb, NULL, 0, 0, TCP_MSS / 2, TCP_ACK, TCP_MSS / 2);
    txcounters.copy_tx_packets = 1;
    test_tcp_input(p, &netif);
    txcounters.copy_tx_packets = 0;
    /* ensure remaining segment was sent */
    EXPECT(txcounters.num_tx_calls == 1);
    EXPECT(txcounters.num_tx_bytes == ((TCP_MSS / 4) + 40U));
    EXPECT(pcb->unsent == NULL);
    EXPECT(pcb->unacked != NULL);
    EXPECT(pcb->unacked->len == TCP_MSS / 4);
    EXPECT(pcb->snd_wnd == TCP_MSS / 2);

    /* verify remainder segment */
    EXPECT(txcounters.tx_packets != NULL);
    if (txcounters.tx_packets != NULL) {
        u8_t sent[TCP_MSS / 4];
        u16_t ret;
        ret = pbuf_copy_partial(txcounters.tx_packets, &sent, TCP_MSS / 4, 40U);
        EXPECT(ret == TCP_MSS / 4);
        EXPECT(memcmp(sent, &tx_data[(3 * TCP_MSS) + TCP_MSS / 2], TCP_MSS / 4) == 0);
    }
    if (txcounters.tx_packets != NULL) {
        pbuf_free(txcounters.tx_packets);
        txcounters.tx_packets = NULL;
    }

    /* ensure no errors have been recorded */
    EXPECT(counters.err_calls == 0);
    EXPECT(counters.last_err == ERR_OK);

    /* make sure the pcb is freed */
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 1);
    tcp_abort(pcb);
    EXPECT_RET(MEMP_STATS_GET(used, MEMP_TCP_PCB) == 0);
}
END_TEST

/** Create the suite including all tests for this module */
Suite*
tcp_suite(void)
{
    testfunc tests[] = {
        TESTFUNC(test_tcp_new_abort),
        TESTFUNC(test_tcp_listen_passive_open),
        TESTFUNC(test_tcp_recv_inseq),
        TESTFUNC(test_tcp_recv_inseq_trim),
        TESTFUNC(test_tcp_passive_close),
        TESTFUNC(test_tcp_active_abort),
        TESTFUNC(test_tcp_malformed_header),
        TESTFUNC(test_tcp_fast_retx_recover),
        TESTFUNC(test_tcp_fast_rexmit_wraparound),
        TESTFUNC(test_tcp_rto_rexmit_wraparound),
        TESTFUNC(test_tcp_tx_full_window_lost_from_unacked),
        TESTFUNC(test_tcp_tx_full_window_lost_from_unsent),
        TESTFUNC(test_tcp_retx_add_to_sent),
        TESTFUNC(test_tcp_rto_tracking),
        TESTFUNC(test_tcp_rto_timeout),
        TESTFUNC(test_tcp_rto_timeout_link_down),
        TESTFUNC(test_tcp_rto_timeout_syn_sent),
        TESTFUNC(test_tcp_rto_timeout_syn_sent_link_down),
        TESTFUNC(test_tcp_zwp_timeout),
        TESTFUNC(test_tcp_zwp_timeout_link_down),
        TESTFUNC(test_tcp_persist_split)
    };
    return create_suite("TCP", tests, sizeof(tests) / sizeof(testfunc), tcp_setup, tcp_teardown);
}
